1. Technical Field
The present invention relates to a technology of cooling a coil.
2. Related Art
A switching power supply such as DC-converter uses a choke coil for smoothing current and boosting voltage. This choke coil is generally constituted by a toroidal coil which has windings wound around a doughnut-shaped toroidal core. The windings of the toroidal coil are exposed on the outer periphery of the coil. Therefore, when the toroidal coil is directly attached to a substrate, wiring pattern cannot be provided on a surface where the toroidal coil is mounted in the vicinity of the toroidal coil for securing sufficient insulation. For increasing the degree of freedom of the wiring pattern, the toroidal coil is attached to an insulating plate member (pedestal), and the coil attached to the pedestal (coil assembly) is mounted on the substrate (for example, see JP-A-6-44123, JP-A-2007-235054, JP-A-2007-234752, JP-A-2005-286066, JP-A-2001-326126, and JP-A-2000-228320).
Since the choke coil included in the switching power supply is disposed on the source current path, a relatively high current flows in the choke coil. Thus, Joule heat is generated on the windings of the choke coil due to winding resistance, and the temperature of the choke coil rises. According to the known coil assembly which has the coil attached to the plate-like pedestal, however, efficiency of cooling the coil is not sufficiently high. This problem arises not only from the coil assembly containing the toroidal coil but also from various types of coil assembly included in the switching power supply and the like.